The new leader of Ukraine's Crimea region says pro-Russian forces control all access to the strategic peninsula and have blockaded all Ukrainian military bases that have not yet surrendered.

Sergei Aksyonov says riot police and security forces have been joined by 11,000 self-defense troops.

All or most of these troops are believed to be Russian, even though the Russian president and defense minister have denied sending in troops.

A U.N. official says a U.N. envoy sent to Crimea to monitor the situation was threatened by up to 15 armed men.

The U.S. Congress is rushing to put in place hard-hitting sanctions on Russia, whose troops have taken over Ukraine's Crimean Peninsula.

The Senate is taking the lead with legislation that would combine loan guarantees to Ukraine's government and measures against Russian government officials, state-owned banks and companies.

It could be introduced as early as next week.